1. Field of the Invention
The present invention relates to a method for controlling a compression ignition internal combustion engine.
2. Description of the Related Art
In recent years, in order to reduce fuel consumption per predetermined load or per predetermined time and a quantity of a discharge in an internal combustion engine, a compression ignition internal combustion engine represented by a homogeneous-charged compression ignition internal combustion engine has been studied. The above described compression ignition internal combustion engine introduces an oxygen-containing gas and a compression self-ignitable fuel into a cylinder, compresses them, and then self-ignites the fuel.
However, the above described compression ignition internal combustion engine has difficulty in controlling the timing of ignition, in contrast to a spark ignition type internal combustion engine. In addition, the above described compression ignition internal combustion engine tends to cause knocking when a demand load of the engine is increased in the case where fuel with high ignitability is used, and tends to cause flame off when a demand load of the engine is decreased in the case where fuel with low ignitability is used. Accordingly, the above described compression ignition internal combustion engine has a problem that a safely operatable range is narrow.
In order to solve the above described problem, a technology has been conventionally known which prepares two types of fuels with high ignitability and low ignitability, mixes both fuels, and supplies the mixture to the above described compression ignition internal combustion engine (for instance, Japanese Patent Laid-Open No. 2004-76736). According to the above described technology, the above described compression ignition internal combustion engine can be stably operated in a wide range of demand loads, by adjusting a ratio between both the fuels to be supplied to the engine in correspondence with the demand load.
However, the above described technology has such inconvenience that two fuels with high ignitability and low ignitability are necessary to be separately charged.